Steve linked to a compilation of monitoring post readings out of the 20km zone: data points
He said,
…but these readings all look low (?). I mean, as far as a level 5 nuclear crisis goes they look low
Actually, I see a different outlier. Notice that the readings are taken by four different groups: JAEA, MEXT, NUSTEC, and TEPCO.
MEXT’s lowest reading is four times greater than any others’ highest readings. It’s responsible for closely bunched points [31], [32], [33]. [32] is by far the highest, the ones on each side of it are lower.
I’m not dismissing this, though. Look at that map and decide what’s the best point to check against MEXT’s data.
…
It’s [46], one of TEPCO’s. It’s closest to MEXT’s readings and nearest the path between them and Fukushima. And on the map it shows 40 uSv/hr. That’s the highest reading apart from MEXT’s. (But in the data box it shows 3.4 uSv/hr. Which is it, guys?!)
What’s the next highest? [2], JAEA’s…which is almost exactly on the line drawn from Fukushima through [32]. Hmmm. The next highest? [1} and [3], which bracket [2]. Double hmmm.
MEXT data is looking more likely. Of course we need more data points (never turn down more data points!). This map tells them where to take them when they get the resources.
Two assumptions, one considerable and one less so: all this data is accurate and the elevated readings are from Fukushima. I’d say the weather carried a fairly narrow band of activity northwest, perhaps listing slightly north early on, but with some westerly swirls further out.
I’m not rejecting this, but nor am I convinced. Aren’t those fallout plumes going the other direction? Maybe there were a few hours when the prevailing wind wasn’t prevailing.
If so, that is a LOT of material laid down.
Will have to wait for the next teaspoon of data.
UPDATE–Hey, wait! Readings [1] [2] [3] were taken first! At 9;20, 9:50, and 10;20. That looks familiar from drills, so I suspect an exhausted RCT team (perhaps in a van) is pausing at select points to take readings. If so, they should also be collecting grass and dirt samples to determine surface contamination, and probably pulling air samples.
Anyway. Best hope? The MEXT team is taking readings on a 10x lower scale than they think they are. But we can’t count on it.
World's Only Rational Man 
MEXT only did 6 of those, from 46. Hmmm… All four teams should measure all 46, that would be interesting.
Well, speaking as someone who would be rounded up for that sort of thing in a catastrophe here, those exhausted teams would probably strangle you for saying that. If they could lift their arms.
Well, being neither a radiological or meteorological specialist, I apologize for what might be a dumb question, but…
Assuming the data are accurate, is there any chance that the helicopter overflights of Dai-ichi for the water dump effort somehow lifted contamination into that rather singular looking northwesterly track of high dose ratings?
People keep apologizing for wanting to learn something! You all must have had strict parents, too.
If you mean do helicopters that overflow smoldering fuel come back contaminated, the answer is “yes”. If you mean contaminated enough to generate millirem/hr. dose rates at places kilometers apart, the answer is “no”. I don’t see the crew as even surviving long enough to get there.
If you look at one of the links Ronny provided, the animation shows the winds doing a clockwise swirl back over those locations, on 3-16. That’s the sort of thing that transports sufficient amounts of material.
But then you have to wonder why all the other readings are so low.
Like most everything we’re getting right now, this data doesn’t answer questions, it raises them.
I know that (apparently small) amounts of contamination are being picked up on the helos and crews.
What I was wondering is more like this. The set of high dose rate readings seem to be on a fairly narrow, and fairly linear, track NW of the plant. The plume models all show the dispersal being primarily NE-to-E, with some variations clockwise from N to S/SW—nothing in the plume models shows a NW track. Also, if it were just normal wind patterns spreading contamination to the NW, then I guess I would expect to see the higher dose rates in a somewhat wider arc than in the linked maps.
So, kind of thinking out loud, I was wondering if the downdraft from the helo blades, or maybe even the static electricity generated by the helos, could have somehow kicked up contamination into a very localized wind path that would account for that narrow, high dose-rate line to the NW.
…and I will have to go back and look at the animations again when I get a chance. I didn’t think the wind patterns looked like they went in the 170 millirem direction, but maybe I didn’t pay close enough attention to the 3-16 data.
Regarding the choppers changing air patterns that much over a number of square kilometers: as a “brute-force effect”, no.
But as a “Butterfly Effect”, certainly!
The problem is that proving which butterfly is the real “culprit” will always be beyond merely human beings.
Re the winds and the “170” area: it looked me that the swirling might have covered it. But only after it had swept clock-wise around those areas that weren’t showing elevated readings.
Of course, if this was in the USA, we could look up the MET data in the emergency plans and see the topography and prevailing winds & projected paths with relative dose rates because its public information in the NRC licensing files… unless its been sealed since 9/11 ?
Might be available in Japanese on their Gov site…
Good point. We changed a lot of stuff after 9/11. If the military could fuzz up GPS data, why not that?